The Vicks Warm Mist Humidifier has 2 power levels to choose from. It produces steam vapor, which is 95% bacteria free. This humidifier has a 1-gallon water tank and can create mist for up to 12 hours on a single water refill. It automatically shuts off once the water reservoir is empty. The water tank can be detached for easy refilling and cleanup. The Vicks humidifier has a reset light to alert you when the tank needs a refill. It has a night light too. This antimicrobial humidifier is ideal for rooms between 1000 and 1200 square feet.